1. Field of the Invention
The present invention concerns a breathable product for protecting articles in mass transportation and cold chain applications.
2. Description of the Related Art
Perishable and temperature-sensitive products such as vaccines or pharmaceutical diagnostics, or horticultural produce such as asparagus or roses deteriorate rapidly when the temperature exceeds certain values by even a few degrees and are, therefore, sensitive to poor temperature management experienced during transportation. Shipping methods for such product have weak points where the cargo is transferred from one means of transport to another, especially at airports where the cargo may be held on the runway while awaiting loading onto an aircraft. To minimize product and financial losses due to temperature excursions during transport, thermal covers may be used to protect a wide variety of cargo, such as flowers, fresh fruits and vegetables, fresh fish, pharmaceuticals and electronic products, from temperature fluctuations experienced during transport.
Many common packaging materials used to protect goods during transport, for example films, stretch films or shrink films, are usually impermeable to gases and water vapor so allow humidity to build up inside the package and condensation to form if the surface temperature changes, and also transmit light of wavelengths from infra-red to ultra-violet, allowing the temperature inside the package to rise rapidly due to a ‘greenhouse effect’ and for these reasons such packaging materials are not ideal for humidity or temperature-sensitive goods.
Many thermal covers comprise two or more layers which may be colored or transparent: a fibrous or foam insulation layer and a PVC, PE or PET outer layer which may or may not be reflective. Other protective materials comprise rigid insulation panels sandwiched between sheets of reflective aluminum or aluminium-coated film resulting in a relatively expensive system which requires additional labour to install and remove and which may only be economic as part of a reusable packing system, adding further to transport costs and supply chain complexity.
Usually multi-layer thermal covers protect pallets of perishable and pharmaceutical cargo during transportation by stabilizing the cargo temperature and shielding the cargo from weather including rain and sunlight damage. Those products help to meet cold chain requirements for specific temperature ranges for typically 2-48 hours, but such covers are not breathable so do not control condensation, and are not generally reflective to sunlight and so can suffer from the greenhouse effect which contributes to a rise in the temperature of the cargo. Such products are multiple-use durable products which are optimized for indoor use, and not for minimizing additional temperature rise due to direct sun exposure or for avoiding condensation. Additionally, they are relatively thick and heavy, making them time consuming to apply to and remove from the cargo and adding to shipping costs both in their contribution to the weight and bulk of the cargo and in the cost of returning them to their point of origin for re-use.
There is, therefore, a need for a lightweight, flexible and breathable cover material which can provide adequate thermal protection as well as protection from rain, at sufficiently low cost to allow single or one-way use during shipping of temperature sensitive goods. There is a further need, where logistics systems allow covers to be returned to the point of origin, for a lightweight, foldable cover which can reduce space and weight requirements on the return journey so providing a more cost effective multiple use cover for temperature sensitive goods.
US 2010/0247855 to Bletsos et al., the content of which is incorporated by reference in the present application, relates to breathable low-emissivity metalized sheets. According to this document, it is known in the art to use moisture vapor permeable (breathable) metalized sheets as house wrap in building construction. The metalized sheets allow moisture vapor to pass through the sheet, thus preventing moisture condensation in insulation that is installed behind the sheet, while at the same time providing a barrier to air and liquid water and enhancing the energy efficiency of the building. In such applications the material is embedded in a roof structure and is not exposed to direct illumination, so its reflectivity is irrelevant to its function, and can even be problematic while the structure is still open during installation as the glare of a very white surface can be disturbing to workers.
U.S. Pat. No. 4,999,222 to Jones et al. describes moisture vapor permeable metalized polyethylene sheets with low emissivity prepared by calendaring a plexifilamentary film-fibril sheet followed by vacuum metallization.
U.S. Pat. No. 4,974,382 to Avellanet describes an infiltration and energy barrier that can be vapor permeable or impermeable having at least one metalized layer thereon.
WO 01/28770 to Squires et al. describes breathable building membranes that include an under-layer of microporous film and a top layer formed of a filamentous polymeric fabric, for example a spunbond fabric, which is provided with a moisture vapor permeable reflective metal coating. While the breathable metalized sheets described above provide a thermal barrier by reflecting infrared radiation, they are susceptible to oxidation of the metal layer upon exposure to air and moisture. An oxidized metal layer generally has a higher emissivity than the corresponding metal and is less effective as a thermal barrier. Such breathable metalized sheets are also susceptible to corrosion of the metal layer upon exposure to acid rain or corrosive ambient conditions such as salt-laden air in coastal and marine environments. In addition, a thin exposed metal layer can be damaged during processing, installation, etc.
European Patent Application No. EP 1400348 to Avril et al. describes liquid impermeable, moisture vapor/gas permeable laminated fabrics that are suitable for use as construction fabrics such as house wrap and roofing underlay that include a reflective film layer formed by vapor depositing a metal layer on a first polymeric film layer and sandwiching the metal layer between the first polymeric film layer and a second polymeric film layer. The film layers protect the metal layer from damage during use, but are moisture impermeable and are microperforated after metallization to provide the desired moisture vapor permeability.
Metalized nonwovens that have been coated with an organic polymer are also known for construction end uses, such as house wrap. However, the polymeric coating is applied using methods that significantly reduce the moisture vapor permeability compared to the uncoated metalized nonwoven sheet.
U.S. Patent Application Publication No. 2003/0136078 to Brown et al. describes a method of insulating a building that includes the step of introducing an insulating membrane comprising a reflective layer and a breathable textile layer into the cavity between the outer cladding layer and the frame. The metalized layer may optionally be coated with a protective layer of plastic or varnish to protect the metal surface.
When a moisture vapor permeable sheet is coated over substantially an entire surface using conventional methods such as air knife coating, flexographic printing, gravure coating, etc., the coating significantly reduces the moisture vapor permeability of the sheet. If the starting sheet has an open structure and is highly air permeable, the sheet can retain sufficient moisture vapor permeability after coating to be useful in certain end uses, such as apparel. For example, fabrics described in U.S. Pat. No. 5,955,175 to Culler are both air permeable and moisture vapor permeable after being metalized and coated with an oleophobic coating. However, when the starting moisture vapor permeable sheet has a highly closed structure with very low air permeability, such as nonwoven and other sheets used as house wrap or roof lining in the construction industry, conventional coatings result in significant covering of the pores on the surface of the sheet. This results in a coated sheet having significantly lower moisture vapor permeability than the starting sheet. This is undesirable in house wrap and roof lining products, which are desirably permeable to moisture vapor while at the same time forming a barrier to infiltration by air and liquid water.
US 2009/0020448 to Emond et al. concerns a method and apparatus for wrapping shipment. Embodiments of the invention described therein relate to a cover, a method of covering, and a cover system to be used with shipments of products transported by air with unit load devices (ULDs). The dimensions of the cover system can vary depending on the ULD they are designed to be used with. The cover system can also be adapted to any individual skid such as wooden or plastic pallets used for smaller loads used in air transport or any other mode of transportation. The cover system can include one or multiple parts that wrap the shipment. Each part of the cover system can be made of one or more layers. Each layer can be made of a single material or a combination of different materials, and different layers can incorporate different materials. The different parts of the cover can be made of different materials or different combination of materials. In specific embodiments, materials used for the cover system are Radio Frequency Identification (RFID) friendly. The cover system provides thermal protection to temperature-sensitive products in or on the ULD. The cover system maintains the proper relative humidity level and gas concentrations (oxygen, carbon dioxide and ethylene) for horticultural product loads. The cover system can also have antimicrobial properties. In addition, the cover system decreases the amount of water vapor released in the cargo holds which is known to affect the reliability of the aircraft smoke detection system and to cause false fire alarms.
Further, in the prior art, a bubble film mostly made of polyethylene or polyester having at least one metallic reflective surface is applied to a cargo so that the metallic reflective surface is facing outwards away from the cargo, in order to reflect infrared components of radiation falling on the cargo from the exterior, and so reduce heating of the cargo.
Other prior art publications include for example WO 2010/006664, US 2010/0092739, US 2005/0042959, WO 01/21871, WO 2005/021824, WO 00/15860, U.S. Pat. No. 5,736,473, U.S. Pat. No. 6,294,222, U.S. Pat. No. 5,316,837, JP 2001 115252 A, JP 04093243, JP 2002 345602 A, JP 2001 317889 A, JP 08049165, WO 2010/107989, WO 2007/021783, WO 2006/024013.
In WO 2006/024013 the content of which is incorporated by reference in the present application, the objective of the described invention is to achieve high moisture vapor permeability (at least 80%) of the initial sheet while achieving a barrier to air and liquid water infiltration and good thermal barrier. That product is suitable for use as a building construction wrap such as roof lining and house wrap.